Structure and Function of Skin Flashcards
What adnexal structures does the skin contain?
Hair
Nails
Glands
Sensory structures
What is the epidermis mainly made up from?
Keratocytes (90%)
What in the dermis is lost as you get older?
Thickness
Where do the adnexal structures lie in the skin?
Dermis
What are the layers of the dermis?
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
What happens as kertocytes mature?
They lose their nucleus and flatten
In normal skin, how long does it take for keratocytes to mature?
30 days
Why is the skin able to regenerate?
Stem cells present in the skin
Where is the stratum corneum thin?
Eyelids
Where is the stratum corneum thick?
Palms and soles
What does the nail help?
Fine sensory motor tasks
Function of the nail matrix
Causes the nail plate (flat keratin) to be generated
What is the cuticle?
Skin at the bottom of the nail
Function of the cuticle
Protects nail matrix from infection
What are the stages of the hair cycle?
Anagen
Catagen
Telogen
Features of anagen
Active growing phase
What % of hair is growing at any one time?
80-90%
Features of catagen
2-3 weeks phase of growth stops / follicle shrinks
What % of hairs are in catagen?
1-3%
Features of telogen
Resting phase for 1-4 months
Old hair sheds and anagen starts again
What % of hairs in a normal scalp are in telogen?
10%
What is telogen pleurium? When would this occur?
A condition where all of the hairs shed at one time
Would occur in a traumatic experience e.g. sepsis
Functions of the skin
Thermoregulation Skin immune system Barrier Sensation Vitamin D synthesis Interpersonal communication
How does the skin provide thermoregulation?
Insulation
- shiver / goosebumps
- contraction of hairs
Heat transfer
What is the skin a barrier against?
Mechanical
Chemical
microorganisms
UV light
What does the skin keep in?
Water
Electrolytes
Macromolecules
What % of the population is affected by a skin disease?
22-30%
Causes of skin disease
Temperature UV Chemical - allergen or irritant Infection Trauma Systemic disease Genetics Drugs
Where is affected in a photosensitivity skin disease?
Exposed sites
- neck line
- arms
Pathology of Bullous pemphigoid
Autoimmune
Desmosomes stop being recognised and immune system comes to attack it
Blistering and epidermis reaches up
Definition of a small skin lesion
< 5mm
Definition of a macule
Small circumscribed area
Definition of a patch
Larger circumscribed area
Definition of a papule
Small raised area
Definition of a plaque
Larger raised area
Definition of a vesicle
Small fluid filled lesion < 0.5cm
Definition of a bullae
Large fluid filled lesion > 0.5cm
Definition of a pustule
Small pus filled
Definition of an abscess
Large pus filled
Definition of an erosion
Superficial loss of epidermis
Definition of an ulcer
Loss of epidermis and dermis
Two types of distribution of a skin lesion
Isolated / solitary / single
Multiple
Another name for hyperlipidaemia
Eruptive xanthoma
Associations of acanthosis nigricans
Insulin resistance
Obesity
Malignancy
T2DM
Where is acanthosis nigricans found?
Flexural distribution
Presentation of acanthosis nigricans
Hyperkeratosis
Hyperpigmentation
Papules
Velvety appearance
What particular skin condition is commonly seen in thyroid conditions?
Pretibial myxoedema
What investigations would be done if a bacterial infection is suspected?
Charcoal swab
- then microscopy, cultures, sensitivities
Can only be used on areas of infected skin and look for weeping areas / ulcers etc
What type of bacterial infection would a charcoal swab not be useful in?
Cellulitis
What investigations would be done if a viral infection is suspected?
Viral swab for PCR
What investigations would be done if a fungal infection is suspected?
Skin scraping
Nail clippings
Hair sample
Then fungal cultures
